The present invention relates to the operating of a switch for manual switching off of an electric current circuit, and more particularly pertains to an operating means with which, in a case of emergency, the current circuit may be switched off and closed again only through a manual activation of the operating means when the emergency situation has been remedied. More specifically, the invention provides improvements on such safety switches in respect of the ability to withstand outer manipulation, and in particular unauthorised dismounting of the installed safety switch.
Herein, the expression xe2x80x9csafety switchxe2x80x9d refers to a separate operating means by which a switch is operated for switching off an electric power circuit.
Safety switches of various types are previously known, by which a restorable switch is operated in emergency situations for disconnecting an electric circuit by hitting or pressing a press button of the safety switch. Connection may be restored through a pulling or turning motion of the button to overcome or avoid the effect of a spring or other locking element that engages a movable portion of the safety switch, arranged for securing the disconnected condition.
A frequent problem in connection with safety switches that are installed in environments that are non-restricted and thus available for the public is damages caused on the safety switch. Such damages may involve unauthorised dismounting of the push button or of the entire safety switch, or manipulation of its function. In all cases the safety switch loses its ability to prevent a dangerous outcome in case of a malfunction of an electrical apparatus. A manipulation of the function of the safety switch may not necessary be detected before the emergency situation arises, thus adding to the risk of a hazardous outcome.
A technical problem in respect of the above said is to design the safety switch in such way, that after installing,. it will be impossible to dismount or manipulate the safety switch without leaving visible damages on the exterior of the safety switch.
It is thus a primary object of the invention to provide a safety switch having mounting means that are inaccessible from the outside when the safety switch is assembled.
According to the invention there is provided an operating means for operating a switch in an electric current circuit, comprising an inner cylinder connected to the switch, a push rod being axially displaceable relative to the inner cylinder between an outer rest position and an inner active position wherein the push rod effects the switch to break the current circuit, and under displacement to the active position the push rod passes and releasably locks into the active position by engagement with a spring member supported by the inner cylinder, and a push button is connected to the push rod for moving the push rod between said positions. An outer cylinder limits the axial travel of the push rod towards the rest position. Upon assembly, the outer cylinder is journalled about the inner cylinder and the cylinders are then mutually rotated to a coupled position in which the cylinders are inter-locked by a snap-lock means that is encased by the superimposed outer cylinder in the assembled position and operative for preventing a relative rotation of the cylinders in the locked position.
Other objects and advantageous embodiments of the invention are further defined in the subclaims and the following description of exemplifying embodiments, respectively.